Experimental determination of leakage current occurring in HgCdTe infrared detectors operating in the mid-infrared

Most of the HgCdTe infrared detectors are fabricated by mesa geometry using a wet chemical or plasma etching techniques. The mesa definition etch process induces undesirable changes in HgCdTe surface properties. In narrow bandgap materials these surface changes could deteriorate a device performance. Uncontrolled band bending occurred on the slopes of the active layer increase of the recombination velocity causing surface leakage current which is a serious problem that affects infrared detectors. Adequate passivation is essential to minimize the effects from the surface states by saturating them. The HgCdTe barrier detectors were investigated for unpassivated and passivated devices. For the unpassivated structure the experimental value of Jbulk (at -0.2 V bias and a temperature of 200 K) was found at the level of 52% of the total dark current for devices with large diameters (500 μm). In the case of detectors with small diameters, the dark current is dominated by the surface leakage current. For a detector with a diameter of 200 μm, the bulk current consists only 28% of the total dark current. After passivation the level of bulk current increase to 58% in cause of 200 μm diameter and almost 75% in cause of large diameter.